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Lowering thrust line on BUSA Phaeton 90

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Lowering thrust line on BUSA Phaeton 90

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Old 02-25-2018, 01:16 PM
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Therapy
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Default Lowering thrust line on BUSA Phaeton 90

Well the title says it all. I am bashing a BUSA Phaeton 90 into a fun scale Curtiss F6C. I'd like to lower the centerline of the wasp radial to better simulate scale compared to original plans. I need some thoughts on this please!

How will this affect the down and right trim of the motor?

What effect should I watch out for for first flight?

I am building this with 1 degree positive on the horizontal stab and 1 1/2 negative on the upper wing.

Need advice on this please.
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Old 03-01-2018, 06:56 PM
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46 views and nobody cares to offer up an opinion on this? Perhaps I should have posted in Scratch builders.
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Old 03-02-2018, 07:18 AM
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I think if you just mount the motor a bit higher or lower with out changing anything else it will not make much difference. If you aren't shimming the motor or mounts the thrust lines shouldn't change. If you were building some real balanced model for competition it might have some changes?

I used to LOVE kit-bashing models, this sounds like a really cool one.. Love to see pics of it as it goes along..or is finished.
I think the plane you are building is a good flier and shouldn't surprise you on the first flight.

So few people build, and very few kit bash.. many people won't post on things they haven't done..
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Old 03-02-2018, 08:50 AM
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I agree with Foodstick that it probably won't make that much difference. I have lowered the engine on sport planes to get the carb closer to the fuel tank centerline without any significant impact on handling. The thing you do have to keep an eye out for is prop clearance. The semi symmetrical wing won't be as likely to balloon under power the way a flat bottom wing would. The amount of right trim shouldn't need to change. I would suggest keeping the incidences per the plans for this particular airplane. The modification of incidences and addition of down thrust is an issue with the BUSA WWI biplanes of similar size due to their flat bottomed wings. Due to their layout a lot of WWI planes have a center of drag that is higher than the thrust line. This tends to lever the nose up under power. With the Phaeton your wings are relatively close together and the airfoil is more tolerant in this regard. Good luck with your build.
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Old 03-02-2018, 09:49 AM
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+1 to whats been said above. Within reason and for a sport airplane, moving the engine a bit shouldn't make that much difference. Enjoy the project!
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Old 03-02-2018, 02:16 PM
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Thank you thank you all for your responses! I felt the worse possible was a little more down trim in the motor. Just looking for other seasoned builder to offer up opinions. Again, thank you all.

I started posting this build in an existing thread. Retrospect, should have started its own thread. It can be found here. balsa usa phaeton 90
I will catch this up if there is interest.

I am getting back after 25 year absence. While I do have 2 foamies to try my skills with without worry (indoor and out) Nothing compares to the feeling of seeing that plane you built take off for the first time. NOTHING. Guess I'm getting old. Happily.
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Old 03-03-2018, 07:51 PM
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Good luck on your build. It looks like you are off to a good start. As long as you keep the airfoils and areas the same and maintain the structural integrity you can tweak the outlines to sorta look like just about any airplane you want. Have fun!
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